The overall objectives of this project are to develop chemical methods which will aid in the characterization and quantification of metabolites removed from uremic patients during hemodialysis. Results of these studies should contribute to a better understanding of the importance of specific metabolites in the uremic syndrome and could ultimately contribute to improved treatment of the uremic patient. Currently, investigations are in progress to develop a high performance liquid chromatographic (HPLC) procedure for separating and detecting guanidine compounds in uremic biofluids. These components are highly suspect as potential uremic toxins. The feasibility of synthesizing and using ion-pairing fluorogenic reagents to separate and determine the guanidines by HPLC is currently under study in our laboratories. In uremic patients there appears to be excessive retention of "middle molecular weight" materials (polypeptide fragments) which are normally metabolized by the healthy kidney. These materials are also suspect as significant uremic toxins. Their exact physiological role in uremia and chemical structure is poorly understood. We are presently examining the molecular weight distribution of components in uremic biofluids by size exclusion and reversed-phase HPLC. A potential HPLC method for sulfhydryl-containing compounds in biofluids is also under investigation. The method involves the use of pre-column fluorogenic derivatizing reagents.